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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:43:11 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:43:11 +0000
commitfc22b3d6507c6745911b9dfcc68f1e665ae13dbc (patch)
treece1e3bce06471410239a6f41282e328770aa404a /upstream/debian-unstable/man7/openssl-threads.7ssl
parentInitial commit. (diff)
downloadmanpages-l10n-fc22b3d6507c6745911b9dfcc68f1e665ae13dbc.tar.xz
manpages-l10n-fc22b3d6507c6745911b9dfcc68f1e665ae13dbc.zip
Adding upstream version 4.22.0.upstream/4.22.0
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.\" -*- mode: troff; coding: utf-8 -*-
+.\" Automatically generated by Pod::Man 5.01 (Pod::Simple 3.43)
+.\"
+.\" Standard preamble:
+.\" ========================================================================
+.de Sp \" Vertical space (when we can't use .PP)
+.if t .sp .5v
+.if n .sp
+..
+.de Vb \" Begin verbatim text
+.ft CW
+.nf
+.ne \\$1
+..
+.de Ve \" End verbatim text
+.ft R
+.fi
+..
+.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
+.ie n \{\
+. ds C` ""
+. ds C' ""
+'br\}
+.el\{\
+. ds C`
+. ds C'
+'br\}
+.\"
+.\" Escape single quotes in literal strings from groff's Unicode transform.
+.ie \n(.g .ds Aq \(aq
+.el .ds Aq '
+.\"
+.\" If the F register is >0, we'll generate index entries on stderr for
+.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
+.\" entries marked with X<> in POD. Of course, you'll have to process the
+.\" output yourself in some meaningful fashion.
+.\"
+.\" Avoid warning from groff about undefined register 'F'.
+.de IX
+..
+.nr rF 0
+.if \n(.g .if rF .nr rF 1
+.if (\n(rF:(\n(.g==0)) \{\
+. if \nF \{\
+. de IX
+. tm Index:\\$1\t\\n%\t"\\$2"
+..
+. if !\nF==2 \{\
+. nr % 0
+. nr F 2
+. \}
+. \}
+.\}
+.rr rF
+.\" ========================================================================
+.\"
+.IX Title "OPENSSL-THREADS 7SSL"
+.TH OPENSSL-THREADS 7SSL 2024-02-03 3.1.5 OpenSSL
+.\" For nroff, turn off justification. Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.if n .ad l
+.nh
+.SH NAME
+openssl\-threads \- Overview of thread safety in OpenSSL
+.SH DESCRIPTION
+.IX Header "DESCRIPTION"
+In this man page, we use the term \fBthread-safe\fR to indicate that an
+object or function can be used by multiple threads at the same time.
+.PP
+OpenSSL can be built with or without threads support. The most important
+use of this support is so that OpenSSL itself can use a single consistent
+API, as shown in "EXAMPLES" in \fBCRYPTO_THREAD_run_once\fR\|(3).
+Multi-platform applications can also use this API.
+.PP
+In particular, being configured for threads support does not imply that
+all OpenSSL objects are thread-safe.
+To emphasize: \fImost objects are not safe for simultaneous use\fR.
+Exceptions to this should be documented on the specific manual pages, and
+some general high-level guidance is given here.
+.PP
+One major use of the OpenSSL thread API is to implement reference counting.
+Many objects within OpenSSL are reference-counted, so resources are not
+released, until the last reference is removed.
+References are often increased automatically (such as when an \fBX509\fR
+certificate object is added into an \fBX509_STORE\fR trust store).
+There is often an \fR\f(BIobject\fR\fB_up_ref\fR() function that can be used to increase
+the reference count.
+Failure to match \fB\fR\f(BIobject\fR\fB_up_ref\fR() calls with the right number of
+\&\fB\fR\f(BIobject\fR\fB_free\fR() calls is a common source of memory leaks when a program
+exits.
+.PP
+Many objects have set and get API's to set attributes in the object.
+A \f(CW\*(C`set0\*(C'\fR passes ownership from the caller to the object and a
+\&\f(CW\*(C`get0\*(C'\fR returns a pointer but the attribute ownership
+remains with the object and a reference to it is returned.
+A \f(CW\*(C`set1\*(C'\fR or \f(CW\*(C`get1\*(C'\fR function does not change the ownership, but instead
+updates the attribute's reference count so that the object is shared
+between the caller and the object; the caller must free the returned
+attribute when finished.
+Functions that involve attributes that have reference counts themselves,
+but are named with just \f(CW\*(C`set\*(C'\fR or \f(CW\*(C`get\*(C'\fR are historical; and the documentation
+must state how the references are handled.
+Get methods are often thread-safe as long as the ownership requirements are
+met and shared objects are not modified.
+Set methods, or modifying shared objects, are generally not thread-safe
+as discussed below.
+.PP
+Objects are thread-safe
+as long as the API's being invoked don't modify the object; in this
+case the parameter is usually marked in the API as \f(CW\*(C`const\*(C'\fR.
+Not all parameters are marked this way.
+Note that a \f(CW\*(C`const\*(C'\fR declaration does not mean immutable; for example
+\&\fBX509_cmp\fR\|(3) takes pointers to \f(CW\*(C`const\*(C'\fR objects, but the implementation
+uses a C cast to remove that so it can lock objects, generate and cache
+a DER encoding, and so on.
+.PP
+Another instance of thread-safety is when updates to an object's
+internal state, such as cached values, are done with locks.
+One example of this is the reference counting API's described above.
+.PP
+In all cases, however, it is generally not safe for one thread to
+mutate an object, such as setting elements of a private or public key,
+while another thread is using that object, such as verifying a signature.
+.PP
+The same API's can usually be used simultaneously on different objects
+without interference.
+For example, two threads can calculate a signature using two different
+\&\fBEVP_PKEY_CTX\fR objects.
+.PP
+For implicit global state or singletons, thread-safety depends on the facility.
+The \fBCRYPTO_secure_malloc\fR\|(3) and related API's have their own lock,
+while \fBCRYPTO_malloc\fR\|(3) assumes the underlying platform allocation
+will do any necessary locking.
+Some API's, such as \fBNCONF_load\fR\|(3) and related do no locking at all;
+this can be considered a bug.
+.PP
+A separate, although related, issue is modifying "factory" objects
+when other objects have been created from that.
+For example, an \fBSSL_CTX\fR object created by \fBSSL_CTX_new\fR\|(3) is used
+to create per-connection \fBSSL\fR objects by calling \fBSSL_new\fR\|(3).
+In this specific case, and probably for factory methods in general, it is
+not safe to modify the factory object after it has been used to create
+other objects.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+\&\fBCRYPTO_THREAD_run_once\fR\|(3),
+local system threads documentation.
+.SH BUGS
+.IX Header "BUGS"
+This page is admittedly very incomplete.
+.SH COPYRIGHT
+.IX Header "COPYRIGHT"
+Copyright 2021\-2022 The OpenSSL Project Authors. All Rights Reserved.
+.PP
+Licensed under the Apache License 2.0 (the "License"). You may not use
+this file except in compliance with the License. You can obtain a copy
+in the file LICENSE in the source distribution or at
+<https://www.openssl.org/source/license.html>.